Biology subjects

Adams, J. D.

Publications and source records attributed to Adams, J. D..

3 recordsLinked to original sources

bioRxiv2024

Vibrotactile auricular vagus nerve stimulation alters limbic system connectivity in humans: A pilot study

Vibration offers a potential alternative modality for transcutaneous auricular vagus nerve stimulation (taVNS). However, mechanisms of action are not well-defined. The goal of this study was to evaluate the potential of vibrotactile stimulation as a method for activating central brain regions akin to other vagal nerve stimulation methodologies. To do so, intracranial electrophysiological signals were recorded in human subjects to perform a parametric characterization of vibrotactile taVNS and investigate changes in coherence across key brain regions. We hypothesized that vibrotactile taVNS would increase coherence between limbic brain areas, similar to areas activated by classic electrical VNS approaches. Our specific regions of interest included the orbitofrontal cortex, anterior cingulate cortex, amygdala, hippocampus, and parahippocampal gyrus. Patients with intractable epilepsy undergoing stereotactic electroencephalography (sEEG) monitoring participated in the study. Vibrotactile taVNS was administered across five vibration frequencies following a randomized stimulation on/off pattern, and sEEG signals were recorded throughout. Spectral coherence in response to stimulation was defined across four canonical frequency bands, theta, alpha, beta, and broadband gamma. At the group level, vibrotactile taVNS resulted in significantly increased global low-frequency coherence. Anatomically, multiple limbic brain regions exhibited notably increased coherence during taVNS compared to baseline. The percentage of total electrode pairs demonstrating increased coherence was also quantified at the individual level. 20 Hz vibration resulted in the highest percentage of responder pairs across low-frequency coherence measures, but notable inter-subject variability was present. Overall, vibrotactile taVNS induced significant low-frequency coherence increases involving several limbic system structures. Further, parametric characterization revealed the presence of inter-subject variability in terms of identifying the optimal vibration frequency. These findings encourage continued research into vibrotactile stimulation as an alternative modality for noninvasive vagus nerve stimulation.

neuroscience↗

bioRxiv2022

Charting a narrow course for direct electron uptake-facilitated electromicrobial production

Electromicrobial production (EMP) processes based on CO2-fixing microbes that directly accept electrons from a cathode have received significant attention in the past decade. However, fundamental questions about the performance limits and viability of this strategy remain unanswered. Here, we sought to determine what would be necessary for such a system to compete with alternative sustainable production technologies based on H2-mediated EMP and traditional bioprocessing with crop feedstocks. Using global warming potential as the metric for comparison, we show that each EMP process can outperform sugarcane-based sucrose production. Following a stoichiometric and energetic analysis, direct electron uptake-based EMP would need to achieve a current density >48 mA/cm2 to reach parity with the H2- mediated system. Because this is currently only practical with a gas diffusion electrode (GDE) architecture, we developed a physical model of the proposed bio-GDE and used it to determine the conditions that a microbial catalyst would experience in a reactor. Our analysis demonstrates that unavoidable inefficiencies in the reactor (e.g., kinetic overpotentials and Ohmic losses) require additional energy input, increasing the breakeven current density to [~]91 mA/cm2. At this current density, the microbial catalyst would need to withstand a pH >10.4 and a total salinity >18.8%. Because currently-known electroautotrophs are not adapted to such extreme conditions, we discuss potential improvements to reactor design that may alleviate these challenges, and consider the implications these results have on the engineerability and feasibility of direct electron uptake-based EMP.

bioengineering↗

bioRxiv2021

A comparative life cycle analysis of electromicrobial production systems

Electromicrobial production (EMP) processes represent an attractive strategy for the capture and conversion of CO2 into carbon-based products. We describe the development and application of comprehensive reactor, process, and life cycle impact models to analyze three major EMP systems relying on formate, H2, and acetate as intermediate molecules. Our results demonstrate that EMP systems can achieve a smaller carbon footprint than traditional bioprocessing strategies provided the electric grid is composed of >~90% renewable energy sources. For each of the three products we consider (biomass, enzymes, and lactic acid), the H2-mediated Knallgas bacteria system achieves the lowest overall global warming potential, indicating that this EMP strategy may be best-suited for industrial efforts based on current technology. We also identify environmental hotspots and process limitations that are key sites for future engineering and research efforts for each EMP system. Our analysis demonstrates the utility of an integrated bioelectrochemical model/life cycle assessment framework in both analyzing and aiding the ecodesign of electromicrobial processes and should help guide the design of working, scalable, and sustainable systems.

bioengineering↗